Multiple mixing circuit for electronic detonation pickups



Allg. 19, 1952 D. R. DE BolsBLANc 2,607,215

MULTIPLE MIXING CIRCUIT FOR ELECTRONIC DETONATION PICKUPS Filed May v,194e 2 sx-xEETs-smfr 1 w moSmEE INVENTOR. n. a DE BolsaLANc BY ATToRNEYs'Ag. 19, 1952 D. R. DE BolsBLANc MULTIPLE MIXING CIRCUIT FCR ELECTRONICDEToNATIoN PICKUPs Filed may?, 194e 2 SHEETS- SHEET 2 N @Px INVENTOR D.R. DE BOISBLANC ATTORNEYS ate'ntecl ug. 19, V1952 2,607,215 f MULTIPLE.MIXING onteurr FQRE'LEC- TRONIC DETONATION PIGKUPS Deslonde R. -deBoisblanc; Bartlesville,V Okla.,

assigner to Phillips Petroleum Company, aicorh.

poration of Delaware Application May 7, 194s.. serial 1%;66.7.8,28Y

vtfclams. l vThis invention relates to electrical circuits for measuringvoltages. In a more specic *aspect it relates to detonation meters thatmeasure peak voltages generated in special pick-ups in internalcombustion engines in response to detonation therein. In anotherspecific aspect it relates to means to select portions of the outputscfa plurality of such pick-ups and mix said outputs. In still anotherspecic aspect it relates to means to graphically or otherwise indicatesaid mix-ture of selected portions.

l `vAs is well understood, knocking in an internal combustion engineresults when theV explosive mixture detonates in an engine cylinder andlarge differences in pressure are generated within the cylinder. Thesepressure waves are con-y verted into sound waves within the cylinder andare reflected back and forth until their energy is dissipated. Thesesound waves are modified by the sound wave components generated as anormal incident to the operation of internal combusti-on engines such assound waves generated bythe operation of the intake and-exhaust valvesof the engine and the pressure waves generated by the normal operationof the engine.

` In my copending application Serial No. 548,757. led August 9, 1944,now Patent No. 2,448,323, for Detonation Meter I disclosed a detonaticnmeter adapted to measure voltages from a single pickup in response todetonatio'n in a. single cylinder of an internal combustion engine.While such asingle'cylinder detonation meter ishighly useful both intesting fuels and in indicating preformance of that oneV cylinder, in avmulticylinder engine, such as an aircraft engine,v it is highly usefulto have an indication oi the preformance of all of the cylinderssimultaneously and preferably continuously. Obviouslythe use ofj acomplete detonation meter as shown in my said copending application foreach cylinder of a multicylinder engine is too expensive andcumoersome,y and also cannot be observed properly as a man cannotobserve a number of dials simultaneously due to limitations common toall human beings, especially if the observer is also engaged in pilotingan aircraft.

In- -the present invention the detonation meter circuit is inoperativeexcept when rendered operative-'momentarily b y a pulse from asynchronized-multivibrator. This multivibrator produces such Ma' pulseeachv time the interruptor in the ignition systemaof the engine producesa spark to' ignite one of the cylinders of the engine. This. results "intherdetonationmeter and' indicators indicating only the detonations'-occurring in *each-cylinderlv as these detonations occur-dura ingv` thelshort duration-of the pulsesA fromtlie Anotherobjee-t is-to provideameans otmixin'g y thev Youtputs of a #plurality ci?L electromagneticpick-ups in such `Ya y manner- .tl-iat only/certain components kwill beobserved. i Another object is to provide a means `o 4.che serving on acathode-ray tubeftheI ti`mesedueiic in which those selectedcomponentsoccur. f

Another object is -toA provide means--wliereby the relativeI detonationlevels of theocylindersof a multicylinderengine may be indicatedt'orpurposes of comparison. Y Y l Y Another object is to provideadetonationmeter circuit only operative when actuated byamulti- Vibratorin turn aetuatedby theignitionfot'each cylinder of amul-ticylinderfengine.

Numerous other objects and advantages will be apparent-to those sklilledin the artupon-reading the accompanying specification, drawings.

In the drawings:` j Y Figure 1 is a schematic'- wiring diagramshowinganrembodiment of the. presentinvention applied to avconven-tionalinternal combustionmgine and conventional ignition system.

Figure 21s a detailedwiringdiagram suitable for use in thedetonationmeter circuit and sy-r' chronized multivibrator? shown inFigure- 1. In Figure 1 a multicylinder interna-l commis-'- tion engineis indicated by a symbolgenerally designated as 3;. -A radial enginehaving'-'c-ylinders is*- shown, but obviously any other multicylinderengine could be used in the `presentinvention; EachV cylinder #hasas-'parkfpl'u 55; the wire rii4 or Whichis-contained A`irl-'heus fflwith' the other wires' 6-,jhutwires ll are not-com nected. Wires liAlead tothe usualY distributor: 8. The usual interruptorv 9- actuated-bwcam-f IU driven by a shaft ofi engine '3 Gshaftnot -showil interruptsthe circuit in wire H'y and condenser `I2 vprevents excess arcingbetween points t3f -I-4. Battery l5 provides currentl in wir -f'lll whenpoints t3 and M1 are closed and'thi marycur-rent ows through aLfew--'turs primary coil inthe usualL sparlecoillffand e# turns throughyWire' Il to battery 115. Thespk claims il and coil IB is really a step'up transformer and contains a large number of turns of a secondary coil(not shown) grounded at one end at I8, the other end being connected bywire I9 to arm 20.

When the primary circuit is broken at I3, I4, by cam I the sudden dropin primary current induces a strong surge of current in the secondary,and this secondary current goes through wire I9, arm 2D, the proper wireB, plug 5, the spark plug gap (not shown) the engine3, ground 2| andground I8 back to the secondary coil. The arm is also driven by anengine shaft which may be the one driving cam I0, and points to theproper wire 6 to fire the proper cylinder 4 at the time the currentpulse comes through wire I9. Parts 3 to 2l are all conventional and anyother engine and/or electric engine ignition system may be substitutedfor them in the practice of my invention. These systems need not beconventional, for example the novelflgnition System of George H.Marmont, patented December ll, 1945, No. 2,390,842, may be employed. In`operating with Marmonts device however a separate wire and a condenserleading from each of wires 90 of his device are ljoined in parallel toWire .24 of my present` drawings tov couple his ignition system and mymultivibrator; instead of the single wire 22, condenser 23 and, wire 24shown in the present drawings when a single spark coil I6 is employed.Magnetoignition may beemployed without invention, in fact any ignitionsystem supplying a pulse to everytime a spark plug fires will embody thepresent invention. v, l

The novel elements of the combination shown in Figure 1 will now bedescribed: e Connected to wire I9 is wire 22 coupled by condenser 23 andwire 24 to multivibrator 25. Multivibrator 25V has a ground 25 and alead 21 coupling it to detonation meter circuit 23.

Each of cylinders 4 kof engine 3 has apick-u 29 mounted `therein in theconventional manner, and each pick-up is connected to the detonationmeter circuit by means of wires 39, collected (but notjoined) by cable3l, each wire vSiivvbeing connected through its respective'isolatingresistance 32 Vto wire33 and thereby to the detonation meter circuit 28.A l

A cathode-ray oscillograph 34 may be connected to circuit 28 by wire 35and may bey grounded at 36. Such oscillographs, are common and thereforeno furtherdescription of the same is deemed necessary, except to statethat on screenr31 waves having time as one coordinate and Voltage orcurrent as the other coordinate: may be viewed momentarily, andthe shapeand size estimated. Il desired lines may be ruled on screen l31 to aidin such estimates of size and shape.

Such cathode-ray Oscilloscopes are ordinarily supplied with a sweepcircuit so that the, electron beam moves very rapidly from one side tothe other of the screen and then lreturns slowly, variations in beamintensityoccurring during this relatively slow return period producing atrace upon the screen. In this apparatus, the sweep frequency may bemanually adjusted'so as to correspond in length to .a complete cycle ofengine operation. Moreover, in conventional oscilloscopes, a terminal isprovided for applying a periodic voltage to the sweep circuit to make itlock in with the frequency of an outside circuit. Evidently, Ain ythepresent apparatus, the sweep circuit may be `locked in with any desiredone of the ignition cables leading to the spark plugs.

This will cause the sweep frequency to have a period precisely equal tothe length of a complete cycle of engine operation. In either case, thetraces representative of detonation in any particular cylinder occupy alocalized region upon the oscillograph screen and, accordingly, theoscillograph enables an operator to determine, in a qualitative manner,the cylinder or cylinders in which detonation is occurring.

YA vacuum tube voltmeter 39 may be connected to circuit 2B by wire 59and grounded at 4I and on the dial 42 thereof the degree of knockintensity may be indicated; for example the peak knock intensity over ashort period of time may be indicated in themanner set forth in my saidcopending application. However the present invention is not limited tothe indication of peak knock intensity by meter 39, as other types ofdetonation indication old in the art may be employed, and circuit 28 maybe varied Aas taught by such other types of detonation indication old inthe art so that 42 will show some other function or parameter of thedetonation. The ground of circuit 28 is indicated at 43.

For the purposes of presenting an embodiment of the present inventionhowever, the peak knock intensity detonation meter circuit of my saidcopending application will be employed for illustrative purposes inFigure 2.

In Figure 2, parts 24, 25, 2G, 21, 28, 33, 34, 35, 35, 31, 39, t3, 4I,42 and 43 are the same as in Figure 1. Parts 25, 28 and 39A are onlygenerally designated as obviously the exact limit or extent of suchelements is inclenite in a circuit diagram as shown in Figure 2. Forexample a certain tube, condenser or resistance could be considered aspart of either unit.

Part 28 may further be regarded as comprising a filter section M, aswitching amplier section 45, and a meter section d1, all connected inseries as stated with the pick-ups 29 connected to the lilter section i4at 33, and the output of the detonation section 41 actuating the vacuumtube voltmeter ft2 by wire 4B. The multivibrator 25 is tied intoV theswitching amplifier section 45 at 21 and the cathode-ray oscillograph istied into section 41 at 35. lThese'sections of .part 28 will now bedescribed. n y Wire 33 is ycoupled to the filter section 44 by couplingcondenser 48. Filter section 44 may comprise a critically coupled bandpass iilter resonant at about 6500 cycles per second comprising atransformer 49 and condensers 50 and 5I. Filter section 44 is. coupledto switching amplifier section 45 by wire 52. This type filter issuitable to the indication of peak knock intensities over short timeperiods. However other lter circuits may be substituted by those skilledin the art, such as a low pass lter allowing the passage of voltageslying below 2,000 cycles when a duplication of the results of the ASTMbouncing pin meter is desirableinone of the material in thissentencebeing shown, but being believed obvious upon consideration of parts I8to `25 inclusive of my copending application Serial No. 629,675, filedNovember 19, 1945, nowv Patent No. 2,534,005 for Detonauon Metersamitier-,nods of Measuring Detonation) Y The switching amplier 45 maycomprise any suitable form of vacuum tube amplifier. As shown the signalon 52 is impressed on'the grid of tube 53 forming the rst stage ofa'conventionally coupled amplienlcoupled by condenser 54 andv resistance55, tov-second stage tube4 56. Other amplifiers may be used, and tubes53 and 56 maybefa single duo-triode tube (such as a 7F7). The gain ofthe amplier is controlled bythe-position of slider 517cm resistance 55Vandsuitable decoupling may be provided at 58-and vv59. 'Tube 56 is-showncoupled'to tube 59a by condenser 60 and.l resistance 6I. yThe amplitudeY of voltage pulses from multivibrator 25 applied to the plate of tube59a is controlled by the positionof slider 62 on resistance 6 I.

Tube 59a is really adiode as thegridis tied to the cathode. Thesubstitution of similar tubes and equivalent circuits obviously lieswithin4 the scope of my invention. Tube 59a prevents the amplifier frompassingv a signal .below a voltage predetermined by the setting ofslider 63 onresistance 64 because the diode 59a will not conduct belowsaid predetermined voltage, and tube 59a. thus actsasa control of thethreshold for the remaining portion of the circuit. In some instancesother switching amplifiers (generally designated as v45) lmay beemployed which do not contain such a threshold, but in the embodimentshown irl-Figure 2, I prefer tor employ such a variable threshold toeliminate small detonations below a predetermined value.

While some indication would be visible on screen 31 without furtherchange in the voltages from tube 59a, it is preferredgtoform sustainedpulses having an amplitude which is a function or parameter of theintensity of detonation as it is easier to see and estimate the value ofthem than to observe the detonation waves themselves. Therefore, I haveincluded arr-exponential pulse generator comprising tubes 65 and 65a.and related partsy coupledl to a sustained pulse generator comprisingtubes 45 and 46a and related parts. Condenser 66 is merely a couplingcondenser employed to eliminate direct current bias which may beintroduced by'diode 59a. Theoutput of diodeV 65a is an exponential formVoltage pulse for the detonation of each cylinder 4 because resistance61 is relatively large. The output of diode 55a is applied to the gridof triode 46 which forms a tuned amplier. The function of said triode 46is to eliminate any remaining voltage fluctuations caused by theintroductionof voltage pulses at 62 from the multivibrator 25, andobviously any conventional tuned amplier or other filter may be employedat this point. Theoutput lof tuned amplifier 4B is converted into-asustained'pulse because resistance 58 is relatively large. Thissustained pulse is applied to cathode-ray oscillograph 34 throughcoupling condenser 69 and appears on screen 31 in readily observableform.

The tuning of amplifier 145 is accomplished by selecting suitable valuesfor condenser lll and resistance 1l. The sustained pulse generated bytube 46 and resistance E8 may lalso be applied to diode 46a of adetonation meter circuit V(generally designated 4'!) where itv isrectified and applied through wire 40-to any standard vacuum tubevoltmeter circuit 39. This voltmeter circuit comprises a tube 39a,milliameter 42, Zero reading adjustment slider 'l2 and meter gain ormeter scale adjustment rheostat '13.

The apparatus is preferably powered by means of a suitable power pack ofwell known form generally designated 14, including full wave vacuum tuberectifier 15 and suitable filter circuit 16. The output is applied onits negative side to ground at 11 and its positive side throughconnection 18 to the various tubes as shown. The heaters in the tubes(not shown) operate on current between ground 19 and point 80V.

This v` leaves only the v`multivibrator "sectionv` 25 tobe described.Multivibrator 25 is triggered byy pulses coming from coil I6`via .Wires22: and 24.. These pulses areapplied across terminal resistance 8| tothe grid of triode 82.

Tube 82 acts as'abuffer to prevent multivibrator 25 from `sendingpulses' back into wire. 24. The'pulses from tube 82 are applied throughconventional coupling condenser-83 to .the .grid

of triode 83al and then through vcondenser 84 ,to the plate of triode85. The multivibratormay be of any known type, but preferably comprisestubes 83a, and 85 with their grids .andgplates cross coupled as shown,which multivibrator (generally designated 25) produces `a uniformamplitude and uniformI amplitude-timex; area pulse Y(not shown) in wire'l1-foreach pulse of anytype received from wire 24. .Itis preferred tousera multivibrator rather than any other type of pulse generator,because, for example, the pulses from coil I6 are so irregular due todifferences in each individual spark plug .circuit 5, 6, etc. that ifintegrated and clipped the pulses generated would be of unequalamplitude-time area.

The pulses from multivibrator 25 are applied to resistance 6| by wire2'!` and slider 52. i

Operation the fuel burned, at a'given fuel-air ratio, but

that detonations of real knocking intensityv are highlydestructive'torthe engine. This information can be used for engine or`fuel test operation of engines, or asan indication of safe cruisingbehavior of the enginev `which is not destructive to the engine.

I.Therefore the operator can watch screen 3 1 to see how the differentcylinders areoperating relative to detonation and read the peak value ofdetonation in the engine on dial 42. i

vThe pick-ups 29 which are constantly picking up all types of pressure'waves and vibrations in the cylinders, are preferably magneto-strictionpressure responsive pick-ups. VThe voltage output of this pick-up issubstantially proportional to the rate of change of pressure in thecylinder. This pick-up generates voltage pulses of various frequenciesfor valve clatter as well as for detonation, as explained more fully inmysaid two copending applications.

These voltage pulses pass through resistances 32 to mix on wire 33 andbe filtered in 'lter 44. While lter 44 is prefera-bly selective to favordetonation vibration frequencies nevertheless some voltages caused byvalve clatter pass through. It is impractical to cut out these valveclatter voltages when they are created by a number of cylinders at onceby a threshold such as 59a, 63, and 64.

Fortunately the detonations occur at a different time than the valveclatter. Therefore by setting threshold 63, 84 high enough to preventthe passage of any voltages from the pickups 29 except when a squarepulse from multivibrator 25 is added at 62, the detonations alone may beselected if the square pulses are produced the right time after theignition spark that the spark voltage changes produced in coil It may betaken from any point on wire i9 and used to trigger the multivibratorthrough wires 22, 24 and the grid of tube 82. 25 therefore produces asquare pulse foreach ignition, and as the time interval of this squarepulse is controlled by the design of the multivibrator 25 I have foundthat these square pulses may be of just sufficient time duration to lastjust as 'long as the detonation voltages from that particular cylinderand no longer.

While the voltages containing only variations due to detonation and veryminor iluctuations introduced by the multivibrator 25 may be taken fromcondenser 66 and run through any cathode ray hook up, or detonationmeter hookup, old in the art, preferably after passage through some sortof lter, such as a tuned amplifier, it is preferred to transform thevoltages from ycondenser 66 into easily visible sustained pulses, easyto see and measure. This is because lthe actual detonation wave form isof such high irequency as to be a blur on screen 31, and the needle ofinstrument 42 could not follow each iuctuation. Y

Therefore voltages from 66 are made into exponential pulses by tube 55and large resistance 61, these pulses are rectied into direct currentpulses by diode 65a, and then made-into direct current pulses of 'longduration (but still having slow exponential decay) by tube l-i'and largeresistance. i lThe shape of these waves is shown in exaggerated manneras line 38 on screen 31.

As fully explained in my said Vcopending application Serial No. 548,757,now atent No. 2,448,323, the circuit shown will make the height of line38, and the reading of meter t2 afunction, or parameter, oiY thepeak-detonation inten'sity over a short period, the period being set asshorter than the time between successive ex- The multivibrator,

plosions ci engine 3 sothat each cylinderzinay make its record on screen31 so that the operator can check the performance of each cylinder VYofhis engine, 'and adjust the fuel-air ratio to the verge of incipientknocking to obtain maximum power ii" desired, or merely observeconditions with or without engine adjustments as he sees rit; Howeverthe present invention is not limited to any particular circuits, or toany values recorded ondial 112, or to any shapes of waves appearing onscreen 3l, and either4 cathode ray oscillograph 313, or voltmeter 39maybe eliminated from some embodiments of the invention. l

be limited only as indicated .by the scope of the appended claims. Y

Having described my invention, I claim:

l. The combination; with an internal combustion engine having aplurality of cylinders, a spark plug in each cylinder, and an ignitionsystem including a source of sparking potential, and a distributor forselectively applying such sparking potential to the respective sparkplugs; of a detonation pickup mounted on each cylinder; detonationindicating means having an input circuit, a threshold device actuated bysaid input circuit, and an output circuit; a plurality of isolatingresistors connecting the respective detonation pickups to said inputcircuit; an output indieating device actuated by said output circuit; apulse generator coupled to said threshold device so that each pulseproduced by said pulse generator causesthe threshold device to becomeoperative to pass signals through said detonation indicating means, saidthreshold device being inoperative when no pulse is impressed thereonfrom said pulse generating circuit; and a single circuit path couplingsaid pulse generating circuit directly to said source of ignitioncurrent whereby each impulse of sparking potential causes a pulse to beproduced by said generating circuit.

2. A device constructed in accordance with claim 1 in which the outputindicating deviceis a vacuum tube voltmeter.

3. A device constructed in accordance with claim 1 in which the outputindicating device is a cathode-ray oscilloscope having at least twopairs of deilecting piates', said oscilloscope being provided with asweep circuit applied to a first pair of deflecting plates, thefrequency of said sweep circuit being such that the cathode-ray beamsweeps across the oscillograph tube once during each cycle or" engineoperation, the signal from said output circuit being applied to a secondVpairl of deiiecting plates whereby detonation in eachoi' said pluralityof engine cylinders provides a deflection of said cathode-ray beam at adis tinct region on the oscilloscope screen.

nnsnonns R. DE BoisBinNc.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS v Date Number Name 1,997,415 Carpenter et al. May2, 1933 2,113,825 Caidwen en a1 Apr. 12, 1938' 2,225,381 Van Dijck Dec.17, 1940 2,292,045 Lancer July 28, 1942 2,319,219 Draper et al May 18,1943 2,337,522 Eldredge Dec. 2l, 1943 2,395,962 Nisewanger et al. Mar.5, 1946 2,403,527 Hershberger July 9, 1946 2,448,322 Pety Aug. 31, 19482,534,276 Lancor Dec. 19, 1950

